Mixers

ABSTRACT

The materials to be mixed are propelled along a first or inlet path which communicates through a plurality of transverse passages with a second or outlet path parallel to the first one and along which they are propelled in the reverse direction. The propelling means may be in the form of screws rotating in bores or gutters. These screws have preferably a frustoconical core in order that the flow of material which they determine decreases in the first path in the direction of travel of the materials and on the contrary increases in the second path. In the case of screws rotating in gutters, the latter may be separated by a relatively low position over which the materials flow regularly from the first or inlet gutter into the second or outlet one.

United States Patent [72] Inventor Pierre Poncet 54, Rue du ProfesseurFlorence, Lyon, France [21] Appl. No. 784,781 [22] Filed Dec. 18,1968[45] Patented Aug. 31, 1971 [32] Priority Dec. 28, 1967 [33] France [31]49,474

[54] MIXERS 5 Claims, 7 Drawing Figs.

[52] US. Cl 259/6, 259/21, 198/213 [51] 1nt.Cl B01i'7/02 [50] Field ofSearch 259/6, 9, 21,25,64, 104; 100/145, 147; 198/213, 214, 217

[ 56] References Cited UNITED STATES PATENTS 319,809 6/1885 Gathman198/213 X 918,494 4/1909 Barr 259/104 1,989,751 2/1935 Hagler et a1. 1198/213 X Primary ExaminerMervin Stein AttorneyAlexander & DowellABSTRACT: The materials to be mixed are propelled along a first or inletpath which communicates through a plurality of transverse passages witha second or outlet path parallel to the first one and along which theyare propelled in the reverse direction. The propelling means may be inthe form of screws rotating in bores or gutters. These screws havepreferably a frustoconical core in order that the flowof material whichthey determine decreases in the first path in the direction of travel ofthe materials and on the contrary increases in the second path. In thecase of screws rotating in gutters, the latter may be separated by arelatively low position over which the materials flow regularly from thefirst or inletv gutter into the second or outlet one.

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SHEET 2 OF 2 MIXERS The present invention refers to mixers for liquid,pasty, pulverulent or fibrous materials.

The known mixers are generally satisfactory when dealing with materialshaving similar physical properties. For instance they operate underrelatively good conditions when it is desired to mix together a numberof viscous substances. But considerable difficulties are encountered formixing a fibrous material with a paste or with a powder.

It is the object of this invention to provide a mixer by means of whichit may be easy to obtain a quite homogenous mixture of materials havingvery different physical properties, as for instance loose fibers and apulverulent or viscous synthetic resin.

The mixer according to the present invention comprises an inlet and anoutlet canal, substantially parallel to each other, through which thematerials being treated are propelled respectively in one and the otherdirection, the said canals communicating with each other by a number ofsubstantially transverse passages provided along at least a portion ofthe length of the said canals.

The material propelling means provided in each canal may conveniently bein the form of a rotating screw. These screws and the correspondingcanals are preferably so arranged that in the inlet canal the flow ofmaterials through a transverse plane decreases along the length of thecanal in the direction of travel of the materials and that in the outletcanal it increases.

In the accompanying drawings:

FIG. 1 is a very diagrammatical illustration of the operation of a mixeraccording to this invention.

FIG. 2 diagrammatically shows a possible construction of such a mixer.

FIG. 3 is a plan view of another embodiment, more particularly forpulverulent or fibrous materials.

FIG. 4 is an enlarged cross section taken along line IV-IV of FIG. 3.

FIG. 5 is a side view of the apparatus of FIGS. 3 and 4.

FIG. 6 is a cross section similar to that of FIG. 3, but correspondingto a mixer more particularly for viscous materials.

FIG. 7 very diagrammatically illustrates a compound apparatus.

In the quite diagrammatical illustration of FIG. 1, the line referencedl designates a first or inlet canal provided with appropriate propellingmeans which propel the materials to be treated towards the right. Themixer comprises a second or outlet canal 2 parallel to the inlet canaland also equipped with propelling means but which displace the materialstowards the left. The materials to be mixed are introduced at 3 into theleft end of the inlet canal in the form of a rough or heterogeneousmixture or of small separate fractions, and the homogeneous mixturerealized by the mixer issues therefrom at the left end of the outletcanal 2, as shown at 4. Canals 1 and 2 are connected with each other bya number of transverse passages 5, the apparatus being so arranged thatthe flow of material is substantially the same through all thesepassages.

As indicated in dashed line at 6 a fraction of the mixture issuing fromthe outlet canal may be recycled into the inlet canal I.

For a better understanding of the operation of the mixer one mayconsider a quite heterogeneous mass M of a number of materials to bethoroughly mixed together. This mass may be divided into a number ofsuccessive heterogeneous elementary masses in, m, m". Each elementarymass is thus itself formed of a quite rough mixture of the materials tobe mixed and owing to the heterogeneous character of the single mass M,the respective proportions of the materials to be mixed are widelydifferent in the elementary masses m, m, m". If these elementary massesare reunited at random, they form another single mass M1 which isobviously less heterogeneous that the initial single mass M since theprobability of the presence of volumes having a composition quitedifferent from the average composition of the whole mess issubstantially reduced.

If new the same operation is repeated with the second single mass Ml,there is obtained a more homogeneous mass M2, and so on. After asufficient number of operations the mass finally obtained may have anydesired degree of homogeneity.

The mixer of FIG. 1 effects automatically the above mentionedoperations. A rough heterogeneous mixture M introduced at 3 into theinlet canal l is divided by the transverse passages 5 into five portionsor elementary masses which are recombined in the outlet canal 2 atrandom or more exactly in conditions wholly different from those inwhich they had been divided from the initial mass M. The product whichissues at 4 therefore corresponds to the single mass M 1. If thisproduct or mass is recycled into canal 1, there will be obtained thesecond single mass M2, and so on.

In continuous operation the product or mixture issuing from the outletcanal 2 is only partly recycled. The'recycled portion mixes with therough mixture introduced into the mixer and already reduces theheterogeneity thereof. The general operation is thus improved.

In the mixer 7 diagrammatically illustrated in FIG. 2 .the materialpropelling means are in the form of screws 8 and 9 rotating within twosuperposed horizontal cylinders which form theinlet and outlet canals 1and 2 of FIG. 1. These cylinders communicate. with each other byappropriately dimensioned orifices 10. The materials to be mixed are fedthrough a hopper 11 into the upper cylinder and the mixed product issuesthrough a lower opening 12 from the lower one. An aperture 13 permits ofrecycling a fraction of this product into the upper cylinder. Screw 9would of course be so arranged and/or driven at such a speed that it mayreceives and propel towards opening 12 and/or aperture 13 the wholequantity of materials propelled by screw 8 from the hopper 11 and/oraperture 13. v

In practical operation it is somewhat difficult to obtain a uniform flowof materials through all the orifices or transverse passages 10. Butthis difficulty may be overcome by so arranging screws 8 and 9 that theflow which they realize through a transverse plane decreasesprogressively in the direction of travel of the materials in the case ofthe screw corresponding to the inlet canal (screw 8) and on the contraryincreases progressively in this same direction in the case of the screwcorresponding to the outlet canal (screw 9). This may be obtained byvarying either the pitch of the screws, or their effective crosssection, or both.

The mixer of FIGS. 3 to 5 comprises an elongated trough 14 formed of twoparallel substantially semicylindrical gutters separated from each otherby an intermediate partition 15 which terminates at a lower level themthe lateral sides of the troughuOn each gutter is mounted a rotatingscrew, each having a frustoconical core, respectively 16, 17, supportinga helical blade, respectively 18, 19 of uniform pitch and with a uniformouter diameter substantially equal to the diameter of the gutters. Thesmaller bases of the frustoconical cores are disposed adjacent the sameend of the trough. The latter is closed by a cover 20 which supports aninlet hopper 21 discharging on the end of screw 16-18 which correspondsto the smaller base of the core 16 thereof. The trough has a loweroutlet 22 below the adjacent end of screw 17-19.

The materials to be mixed are loaded into hopper 21. They are propelledtowards the right in FIG. 3 by screw 16-18, as indicated by the arrow.Owing to the increasing diameter of core 16, these materials overflowthe upper edge of partition 15, and they are taken by screw 17-19 andpropelled towards outlet 22. The transverse flow of materials from screw16-18 into screw 17-19 extends uniformly along substantially the wholelength of partition 15.

When it desired to recycle a portion of the mixed product from screw17-19 into screw 16-18 at the left end of the mixer in FIG. 3 it issufficient to throttle the outlet 22, as for instance by means of aslide valve. The product accumulates at the left end of screw 17-19 andit overflows partition 15 so as to be reintroduced into screw 16-18.

It is obvious that the same results could be obtained with screws havinga core of constant diameter, but a pitch decreasing from left to rightin FIG. 3, or with screws having a decreasing outer diameter, thecorresponding gutters being correspondingly shaped.

The mixer of FIGS. 3 to 5 is particularly adapted for freely flowinggranular or fibrous materials or even for liquids. It is not suitablefor pasty, tacky or viscous substances.

FIG. 6 illustrates an embodiment which differs from the mixer of FIGS. 3to 5 in that the gutters are replaced by cylindrical bores provided in acasing 23 which closely surrounds the screws 16-18 and 17-19, thesebores communicating through transverse passages such as 24. Such anapparatus is particularly efiicient with viscous materials which tend toadhere to the surfaces of the casing or of the screws. The inlet hopper21 may be replaced by a preliminary mixer, such as a mere screwconveyor, which feeds the apparatus with a rough mixture of thematerials to be treated.

FIG. 7 illustrates a compound apparatus which may be considered asformed of two elementary mixers of the kind of FIGS. 3 to 5 disposed inseries. The first one comprises two parallel screws 162-] 8a and 17a-l9awith frustoconical cores. The second one is formed of screws l6a18b and1712-19 also with frustoconical cores. Screws 16a-l8a and 16b -l8b aredisposed in line, the smaller bases of their cores being rigidlyconnected with each other by a short cylindrical portion 25 alsosupporting a helical blade. In the same manner screws 16b-18b and l7b19bare in line with the smaller bases of their cores assembled by acylindrical portion 26. The respective positions of the inlet hopper andof the lower outlet have been very diagrammatically indicated at A andB.

The screws rotate in two parallel gutters separated by an intermediatepartition 15, as in the case of FIG. 4.

The material loaded at A are submitted to a first mixing step by screws16b-18a and 17a-l9a then to a second one by screws l6b-18b and 17b-19aThe mixed product issues at B and if the outlet is partly closed, aportion of this product is recycled from B to A.

It would of course be easy to imagine a large number of otherarrangements of compound apparatus formed of any number of elementarymixers disposed in series.

I claim: I

l. A mixer for materials to be mixed comprising:

a. a first canal extending between a first end and a second end, withsaid first end forming an inlet to receive said materials;

b. a first propelling screw of the variable flow type rotating in saidfirst canal to propel said materials from said first end towards saidsecond end with a progressively decreasing flow rate;

c. a second canal substantially parallel to said first canal, saidsecond canal extending between a first end and a second endin adirection opposed to said first canal, with said second end forming anoutlet for said materials;

d. a second propelling screw rotating in said second canal to propelsaid materials from the first end of said second canal to the second endthereof with a progressively increasing flow rate;

e. and transverse passage means provided between said first and secondcanals along the whole length of said first and second screws;

whereby the excess of materials resulting from the progressivelydecreasing flow rate in said first canal is positively introduced intosaid second canal in correspondence with the progressively increasingflow rate insured in said second canal.

2. In a mixer as claimed in claim 1, said first screw being ofsubstantially uniform outer diameter and having a frustoconical core ofprogressively increasing diameter between the first end and the secondend of said first canal. I

3. In a mixer as claimed in claim 1, said second screw being ofsubstantially uniform outer diameter and having a frustoconical core ofprogressively decreasing diameter between the first end and the secondend of said second canal.

4. In a mixer as claimed in claim 1, said passage means comprising asingle passage extending along the whole length of said first and secondcanals.

5. In a mixer as claimed in claim 1, means to recycle a portion of saidmaterials from the second end of said second canal into the first end ofsaid first canal.

1. A mixer for materials to be mixed comprising: a. a first canalextending between a first end and a second end, with said first endforming an inlet to receive said materials; b. a first propelling screwof the variable flow type rotating in said first canal to propel saidmaterials from said first end towards said second end with aprogressively decreasing flow rate; c. a second canal substantiallyparallel to said first canal, said second canal extending between afirst end and a second end in a direction opposed to said first canal,with said second end forming an outlet for said materials; d. a secondpropelling screw rotating in said second canal to propel said materialsfrom the first end of said second canal to the second end thereof with aprogressively increasing flow rate; e. and transverse passage meansprovided between said first and second canals along the whole length ofsaid first and second screws; whereby the excess of materials resultingfrom the progressively decreasing flow rate in said first canal ispositively introduced into said second canal in correspondence with theprogressively increasing flow rate insured in said second canal.
 2. In amixer as claimed in claim 1, said first screw being of substantiallyuniform outer diameter and having a frustoconical core of progressivelyincreasing diameter between the first end and the second end of saidfirst canal.
 3. In a mixer as claimed in claim 1, said second screwbeing of substantially uniform outer diameter and having a frustoconicalcore of progressively decreasing diameter between the first end and thesecond end of said second canal.
 4. In a mixer as claimed in claim 1,said passage means comprising a single passage extending along the wholelength of said first and second canals.
 5. In a mixer as claimed inclaim 1, means to recycle a portion of said materials from the secondend of said second canal into the first end of said first canal.